Since nothing in the federal or state constitutions expressly requires the governor of California to act on commutation petitions within a set timeframe, it's fairly clear that the governor can take as long as s/he wants on these petitions -- including, essentially, forever.
But to the degree it was unclear before, today's Court of Appeal opinion expressly so holds.
I did learn one thing today, however, that I didn't know previously. Apparently, the California Constitution says that the governor can only grant a pardon or commutation to someone "twice convicted of a felony except on recommendation of the Supreme Court, 4 judges concurring." (Article V, Section 8).
I'm quite confident that others knew about this quirk in the California pardon scheme, but I didn't. I was more familiar with the federal system, where the president can do whatever s/he wants.
Interesting wrinkle.
